HDU 3461 Code Lock

#include <cstdio>
#include <iostream>
using namespace std;
const int mod=1000000007;
long long t;
int f[10000010];
int sf(int x){return x==f[x]?x:f[x]=sf(f[x]);}
int Union(int x,int y){
x=sf(x),y=sf(y);
if(x==y)return 0;
f[x]=y;
return 1;
}
long long power(int x){
if(x==0)return 1;
long long t=power(x/2);
t=t*t%mod;
if(x%2==1)t=t*26%mod;
return t;
}
int main(){
int m,n,a,b;
while(scanf("%d%d",&n,&m)!=EOF){
for(int i=1;i<=n+2;i++)f[i]=i;
int ans=0;
while(m--){
scanf("%d%d",&a,&b);
ans+=Union(a,b+1);
}
cout<<power(n-ans)<<endl;
}
}